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Tbilisi (English: tə-bih-LEE-see, tə-BIL-ih-see; Georgian: თბილისი [tʰbilisi] (listen)), in some countries also still known by its pre-1936 international designation, Tiflis ( TIF-lis), is the capital and the largest city of Georgia, lying on the banks of the Kura River with a population of approximately 1.5 million people. Tbilisi was founded in the 5th century AD by Vakhtang I of Iberia, and since then has served as the capital of various Georgian kingdoms and republics. Between 1801 and 1917, then part of the Russian Empire, Tbilisi was the seat of the Imperial Viceroy, governing both Southern and Northern Caucasus.
Because of its location on the crossroads between Europe and Asia, and its proximity to the lucrative Silk Road, throughout history Tbilisi was a point of contention among various global powers.
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The Sun is the star at the center of the Solar System. It is a nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy mainly as light and infrared radiation. It is by far the most important source of energy for life on Earth. Its diameter is about 1.39 million kilometres (864,000 miles), or 109 times that of Earth, and its mass is about 330,000 times that of Earth. It accounts for about 99.86% of the total mass of the Solar System.
Roughly three quarters of the Sun's mass consists of hydrogen (~73%); the rest is mostly helium (~25%), with much smaller quantities of heavier elements, including oxygen, carbon, neon, and iron.The Sun is a G-type main-sequence star (G2V) based on its spectral class. As such, it is informally and not completely accurately referred to as a yellow dwarf (its light is closer to white than yellow). It formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into an orbiting disk that became the Solar System. The central mass became so hot and dense that it eventually initiated nuclear fusion in its core. It is thought that almost all stars form by this process.